Tide Pooling Log: Kayaking Southern California’s Mudflats
Not all intertidal landscapes are as beautiful to explore as rocky shores. Some require a little more extra —- and a willingness to get dirty.
After several days of visiting rocky and sandy shores, I decided to take advantage of the low morning tides by exploring a muddy shore in an estuarine environment. Because the area we were visiting is protected and walking on muddy shores can significantly alter the environment, we opted to kayak instead of exploring on foot. Most of the shoreline was islands anyway and required a boat to get there.
Kayaking the intertidal is a great way to lower your impact on calm sandy or muddy shores while searching for animals. Kayaks can function in the shallowest of water, less than a foot deep for some boats, so you’ll have a great view of any intertidal life on the bottom. Many protected areas offer kayak rentals as well.
This particular bay is one of the few wetlands that remain in California, even though they used to cover most of the coastline. Essential carbon sinks and biodiversity hotspots, they present a unique opportunity to peer into a coastal California that is all but non-existent today.
The tide was only moderately low this morning, maybe 0.7ft or so, but much of the salt marsh was still exposed, and layers of mud below where terrestrial plants dropped abruptly into the water in tiny cliffs. As we started out on the glassy, morning water, we could see eelgrass beds below us. They seemed to lack much of the diversity of the previous eelgrass beds I visited on sandy shores, but then again, they were a little deeper and it was difficult to see. I moved closer to the shore to get a better view but they gave way to flat mud once I was in less than a foot of water.
Muddy shore animals change their habitat more than other intertidal animals. The mud grains are so fine that a crab can create a rather permanent burrow and the trail of a snail along the surface can be traced many yards. All around there was evidence of animal life in burrows, trails, tiny pellets of sand, and mounds of sediment different in color and texture than the surface mud, likely excavated from below the surface.
The first and most abundant animal we saw was these shores was a species of Nassa mudsnails, probably channeled basket snails (Caesia fossata). With an excellent sense of smell, these snails prowl around the mud’s surface searching for food to scavenge. Although abundant, they were quite beautiful with black and white speckled feet. One that I picked up was able to right itself with its strong foot and crawl across my palm back to the mud.
This large group was feeding on a dead fish. These “clean-up crew” services are vital to the health of the ecosystem as they move the energy in organic matter back into the food chain.
Among the snails, I noticed a most unusual creature for muddy shores: fairy palm hydroids (Corymorpha palma). These delicate cnidarians are related to anemones and coral and lack any hard body parts. Swaying in the current no more than an inch or two tall, they filter tiny organic particles from the water. When the tide is low, they lose their shape and lie limp on the sand. It seems like so delicate a creature might die upon being exposed but apparently suffer no harm.
I also saw several sacks of Navanx eggs while kayaking in this bay, but no adult specimens. Perhaps they were in deeper water or blended in with the dark sand.
Clams are known for being the most common invertebrate to find on muddy shores. Burrowing deep in the substrate, they often lie unseen by both tidepoolers and predators. While there were shells galore, I only saw a couple of live bivalves and I wasn’t able to nail down identification on many of them. The one on the left is most likely a species of Venus clam while the one on the right appeared to be in the mussel family.
Speaking of shells, I was paddling along the shore when I thought I spied a shell I recognized. Slowly maneuvering my kayak back around, I scoped up the thin shell of a cloudy bubble snail (Bulla gouldiana). I had seen egg-laying masses earlier in the week at a sandy eel grass bed but didn’t see any adults here.
Several burrowing anemones, no more than an inch across, were scattered around the mud flats in shallow water. This one pulled into itself when my boat drifted over it, suggesting that they might retreat under the mud completely if above the low tide line. I am also unsure of the ID on this anemone, but the horizontal white bands suggest that it is perhaps a moonglow anemone (Anthopleura artemisia), well known for burrowing in our coastal waters.
Above the water line, the mudflats were dominated by the California horn snails (Cerithideopsis californica). Growing and reproducing in the spring and summer and going dormant in winter, these snails were lying on the mud in the thousands, patiently waiting for the tide to return. The photo on the right has about a hundred of these animals. They feed mostly on benthic diatoms and are very hardy creatures, tolerant of very low salinities and long periods of exposure to air.
We also the burrows and the tiny forms of the now very unusual Mexican fiddler crabs (Leptuca crenulata), easily recognized by their one relatively enormous claw. Once common in California, the destruction of wetlands has decreased the ranges of these burrowers so that they are now only found in a few estuaries and wetlands. Incredibly shy creatures, they snap into their burrows the moment you get too close. Although we didn’t have our large cameras with big zooms, we nudged the noses of our kayaks onto the mud and watched the crabs from a distance. There are at least ten in the photo below.
As many of 15 were all standing by the opening to their burrows, waving their larger claws, extending them to their full length, and then snapping them back toward the body. One would wave and then the next would. I have read that the motion is displayed to attract females, who do not have an abnormally large claw.
There were also several birds about. A resident yellow-crowned night heron (Nyctanassa violacea) was hunting along the shoreline, along with several great blue herons (Ardea herodias) and snowy egrets (Egretta thula). A flock of black skimmers (Rynchops niger) was also meandering about, skimming the shallow waters for small fish, and a large brown pelican (Pelecanus occidentalis) watched us from his bouy perch.
Before hauling into the shore, we took a quick look at a nearly seawall. The tide was probably over a foot by now, but several Pacific oysters (Magallana gigas) were still exposed with many more beneath the water just below them.
A variety of mussels and barnacles were living on their shells. You often see this on seawalls that are too smooth for many sessile animals to take hold. But when one animal (like an oyster) begins growing other animals grow on top of it.
I took many photos of this strange thing settled on an oyster before I realized it was a bay blenny (Hypsoblennius gentilis), still as a statue, resting on the lip of the shell.
The tide could hardly be called low by the time we paddled back to the beach and rinsed the boats. I’m excited to visit this location again at a lower tide to find more invertebrates.
#Kayaking #Southern #Californias #Mudflats #Tidepooler
